Method of testing for stereopsis



April 9, 1940.

RA A. SHERMAN i IETHOD 0F TESTING FOR STEREOPSIS Filed Deo. '4. 1955 2 Sheets-Sheet 1 KsY-7JUB/4 F l I 'vm-S2M s Z L E Y l I FHS-'4 MMM INVENTOR.

A TTORNEYS.

R. A. SHERMAN ITHOD 0F TESTING FOR STEREQPS'IS Filed Dec. 4, 1935 sneets-sheet 2 IN VEN TOR.

Puentes Apr. a, 1940 UNITED. sTA'rEs PA'rlsNjl' ori-lcs y 2.199.905 I manon or ns1-me roa smaorsls l lneuen a. sha-mm. Meadville. Keystone' View Company. Mead VVeel|mrati0n-`ef Pennsylvania assigner tol ville, Pa., a

Application December 4. 19:5. semi No. 52,198 zum (ci. ca -zo) Ihe mostcommon method oi for depth from him. The pegs are separated and the .w

eilort given to thepe'rson being tested is to manipulate the pegsv through the cordtoward or from him so as tobringthe pegs' at 'even distances from him. Such tests were mademore necessary i'or the requirements of aviation, and there was established by the army Va passing test ot 30 millimeters of. separation between the pegs, this having beendetermined after a large number o! tests to be the average ability oi aviators of known ability in-ilying. This diiierence represents an angular dlii'eren' of 10 to 12 seconds oi' arc. Some individuals 'were foimd to besensitive to diilerences as little as 3 seconds oi arc.

The present invention was designed to simplify these tests and to provide a rating for the person being tested with'relation to the known standard. In carrying outA the invention la series of slides or stereopticon views are made, carrying targets arranged in pairs on the fields of the slides or views, one pair oi targets being oilset relatively to another pair or lpairs of. targets to correspond to the distances oi' those targets from the camera making-the views. In-maklng the views, therefore, so as to give a quantity rating, it is only.

necessary lto have a series of views varying the distances toward and i'rom the camera of pairsA of targets, thus giving to the views the stereoptic distance eii'ect incident to the variation in distances between the pairs oi' targets and the camera. 'Ihe person being tested, as these views` this rating can be designated on the various' views which are presented to him so that the test may be accurately carried out with very simple surroundings and Vconvenient apparatus.` i

Features and details of the invention will ap-A pear from the specification and claims. n

A preferred embodiment ci the apparatus involved in the invention and with which the method may be practiced, is illustrated in the accompanying drawings as follows:

liig. l shows an elevation of a screen having variolu targets arranged thereon in series some otwhich are advanced toa predetermined distance in iront of the screen.

Fig.) shows a pian view of the same screen and'targets; l

Fig. 8 shows a diagramnindicating the stereopable symbols being letters and"numera1s.

ng. 4 shows s diagram indicating the an`gular eiiects recorded on a stereoscopic camera by images or targets variously placed toward and from the camera, the angular relation and lens distances being exaggerated. Fig. 5 shows a plan view oi an ordinary stereoscope. V

,Fig. 46 shows a side elevation ot the stereoscope. Fig. "l shows an elevation oi one oi'the slides 'or stereopticon views, prepared in accordance with the invention.

i marks a screen and I horizontally arranged white back-grounds ordinarily formed with white enamel nished paper. A seriesoi targets 3 are placed on each of these back-grounds. the prefer- One target 4 of each series mountedlon an individual paper card 5 is advanced forward from the screen a predetermined distance. This adjustment of the advanced target 4 is mounted on a wire 8 whichextends directly forward fromthe screen so that the target may, by merely sliding it along on the wire,'be adjusted to any denite predetermined distance iromthe screen.A Dif-,-

.ferentv wires are provided for diierent targets for different slides. The targets 4 of each vfiv or slide are arranged ait the same distance froml made with the stereopticon camera 9, this camera being ordinarily set l2 feet from the screen. This is not a necessary distance but a convenient distance from which to scale differently ranged stereopsis conditions.

As noted inFig. fi, a stereopticon camera 9 has the lenses i0. These lenses are usually adjust-,-

able, but the o dinary average separation is about 8 centimeters. A sensitive plate Il in the illustration is placed 20 centimeters from the lenses.

Taking the target .l on the screen as the full or zero distance of comparison, it will be noted that the offsetting of the two images J on the plate will indicate an image distance of'1'2 feet l 'from the camera. This oil-setting of the images on the plate being the separation oi' these images in accordance with the angular lines from the image J to the image as carried through the lenses to the plate.

The targets H in Figs. 1 and12,v assumedl to be the nearest to the person being tested of any setting which with the scale thatl has'been adopted, is 813 mm.,and the oil-setting oi.' the image 'H'H' on the sensitive plate reilected from the ierred from the plate to the slide or view I 3 asA it E printed from the plate. Thus, the person being tested, observing the view it through a stereoscope i2 is subjected to offset variations in the targets on the slides or views which correspond to angular variation to which he would loe subjected viewing the actual images arranged on the screen, and with the point or view at the same position as that of the camera.

With this hach-ground it has been possible to Work out a series of arrangements of targets which will give quantity rating corresponding to ratings which may be accomplished with the peg test heretofore referred to. In developing this -feature of the invention it was found that tests made with a great many individuals having deiinite ratings, as with the peg test, it was oiuid that persons who were sensitive to 3 seconds of arc difference on the'peg test could detect no smaller than idf: seconds i arc difference on the stereornetric slides, and that those who detested 10.5 seconds of arc diference on the peg test ivere sensitive to only 19 seconds of arc difference on the stereoinetric slides. .For this eason i9 seconds of are dierence was taken as he stereonietric equivalent of 10.5 seconds on the pegs and was adopted as the practical starting point, or '168 rcent rating. It is therefore incre than i0!) percent stere- .he curveoi least diterences established, similar to the curve ci visual acuity f 'oy those in this art as authoritative, csitioiinig o the targets for progressive ratings he rec., ly worked out. 'n Fig. 3 this curve plotted at l showing the distance along "he wires that targets are placed for each ating viene longestA distance from the creen being SLichierici the least distance l illirneters. These .ratings have been computed as follows, and the numbering of the views as ordinarily used is indicated hy a number on the slide:

The

innig/sis of' the stereometrz'c unit p, ,Cmds Separation Distance ci Slide To C15, E am on plates, letters from mm. screen, nim.

l 1, 300 l. C0 813 2. 5 870 67' 500 EL i0 GOO 45 C6 'L l5 440 34 305 5. 2i) 360 28 125i S, 28S 22 263 7. EU 210 1S 152 8. 35 175 135 3.27 3. e 140 1013 100 10- 'i5 115 O0 32 ll. 5D 95 075 5T 1E. E5 80 G62 66 i3. CG 75 059 5G 1L 65 65 G5 45 l 70 55 O 3S l 75 45 G35 32 1L. 3i) O3 25 1S.- 85 32 O25 21. M 9() 26 02 16 204.-- 95 21 O16 13 2L. 100 19 .0145 10 224. 105 13 0l 7 23 110 10 008 4 There is shown in Fig. '7 a slide or view i3 result-mg from a target setting as indicated in l and 2. There is also shown in dash lines Fig. 2 a target setting for a slide #9, as indicating in the above list, which places the targets 100 millimeters from the screen. There is one slide for each rating and a setting of targets in making the slide corresponding to the target distances as indicated in the table.

Preferably the characters are of different sizes, ranging in height from V4" to 1%?. The purpose of varying sizes of the letters on the targets s to prevent any possibility of assistance in identifying the position of the letters through diierences in actual image sizes. Dierent slides also have diierent arrangements ci characters; thus the slide having the targets as indicated in the dash lines might have characters substituted for the characters of U, T and R, and these could be of various sizes so that there would be no assistance to the person being tested in his response to the angular difference incident to an offsetting of the letters on the views. This invention, therefore, involves a very simple but accurate method of procuring the various photographic plates from which the views may be made. It avoids any complicated computations and assures absolute accuracy, assuming that the camera is accurate, and it also assures a correct rating of the person observing these views. It also provides these vietvs which have the proper setting of the targets relatively to each other to accomplish an accurately measured rating for the person being tested. All that is necessary is to submit the views one after the other and without particular rotation, until 'the view involving the least distance diierence of the targets can he recognized by the person. This gives him his rating.

With some persons their stereopsis sensitiveness diiiers with the position of the target up or down. For this reason the lthree series of targets are arranged horizontally, one above the other,

so that the person being tested can be tested not only with relation to targets directly in front of his eyes but also as to targets having a slight inclination to 'the line of vision above and below the direct position.

lFhat I claim as new l. The method of making stereopticon views for 'testing stereopsis which consists photographing stereoptically pairs of targets, placed at'predetermined distances from the camera and each other, the images of the targets on the iields thereof, having a pre-established offset adapted to determine by observation in a stereoscope a degree of stereopsis capacity.

2. The method oi' making a series oi' Stereopticon views for testing stereopsis, which consists in photographing stereoptically for each view pairs of targets placed at predetermined distances from the camera. and each other, the images of the targets on the elds thereof having a pre established offset adapted to determine by observation any degree o1' stereopsis capacity, the targets from which each View of .the series is taken being diil'erently spaced in predetermined relation to the spacing of the other views.

REUEL A. SHERMAN. 

